This invention relates to a combination lock for vaults, safes or the like and is of the type in which the combination is arbitrarily changeable; the opening movement of a locking bolt is effected by manually turning a bolt-operating knob after the set combination is properly dialed; for each digit of the combination a locking bar is provided which, in case the set combination was improperly dialed, prevents the opening motion of the locking bolt; and the visible display of the dialed combination disappears during the opening motion of the locking bolt. It is noted that the term "dialing" is intended to include a shifting (linear) displacement of the digit-bearing lock component or components into the position corresponding to the set combination.
A combination lock for vaults, safes or the like has to meet essentially the following requirements:
(a) The possibility of setting or changing the combination without a disassembly of the lock;
(b) Protection against monitoring the combination by scanning or listening;
(c) Preventing the locking bolt of the combination lock from opening in case of improper dialing of the combination and/or by force;
(d) Cancelling the visual display of the combination as early as the opening motion of the locking bolt.
In a known combination lock disclosed, for example, in German Pat. No. 2,552,789, for the opening of the locking bolt a manipulator is provided which also serves for dialing the combination. A number of gear wheels rotatable by the shiftable manipulator are mounted in series on the shaft of the manipulator. Each gear wheel meshes with a toothed rack having notches into which locking projections of a tumbler mechanism may extend. The tumbler mechanism has a plurality of immobilizable tumbler plates on which the locking projections are provided and which are assigned individually to the toothed racks and combined into a raising and lowering unit held in a disengaging position by return springs. The unit carries a locking pawl which immobilizes the locking bolt in the disengaging position. For shifting the locking plates for the purpose of resetting the combination, an eccentric pin coupled in the shifting direction with the raising and lowering unit is provided with an actuating head which, after opening of the door served by the combination lock, is accessible through an opening in the lock housing. The manipulator may be coupled with a bolt-actuating disc having actuating components such as entraining projections, ribs and a slot in such an arrangement that upon rotating the manipulator subsequent to dialing the combination, the raising and lowering unit is moved, in an initial rotational phase, into the engaging position against the force of the return springs. In the engaging position, the locking projections extend into the notches of the toothed racks and, as a result, the locking pawl releases the locking bolt. Upon rotation of the manipulator (after clearing the locking arrangement) beyond a predetermined position, the display of the combination visible from the outside is cancelled. Upon further rotation the locking bolt is retracted, whereby the raising and lowering unit is released and is moved rearwardly by the return springs into the disengaging position.
The known combination lock of the above-discussed type is disadvantageous in that it has a cluttered construction; it is circumstantial to set and to dial the combination; the device which cancels the display of the combination is complex; and the lock mechanism operates with a great number of movable components without improving operational safety and security.